Aircraft: EMBRAER JET UNDIFFERENTIATED OR OTHER MODEL
Phase of flight: Climb
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Other / Unknown

March 2013; an Embraer aircraft was released for a Functional Check Flight (FCF) flight where they found the ailerons stiff and about thirty minutes into the flight they were unable to engage the Aileron Trim System the FCF was canceled and returned to ZZZ. Whereupon further investigation it was found that the flight deck Aileron Control Cables were over tensioned. I [had] started the Aileron Cable Rigging Task on [approximately] eight days earlier at around XA:00am. I checked the rig pins to make sure they were all installed and checked the temperature in the aircraft near the control cable as per Aircraft Maintenance Manual (AMM) 27-11-01. I compared the temperature; it was 71-degrees; to the Cable Load Chart which was 94-lbf (pounds foot); plus or minus five pounds (lbs) for the Hand-wheel [Control Wheel] and 112-lbf; plus or minus five pounds for the Wing and Fuselage cables. With the GSE-074 Tensiometer; I checked the tension on all the aileron cables and found them all to be out of limits. At that time I proceeded to adjust the cables in the Flight deck area to the 94-lbs plus or minus 5lbs; as listed on the chart; then I moved on to the wings and fuselage areas and adjusted them to 112-lbs plus or minus 5lbs.By the time I got the wings and fuselage [cables] ready to run them through; the temperature had dropped due to the hangar doors being opened up. So I unpinned the cables and ran the controls through ten times and repined the cables and rechecked the chart for the new temperature and found them to be out of limits again. I noticed when I was rechecking the cables that the cables were not setting in the Tensiometer like they should be; so after a closer look at the Tensiometer I found the body was coming apart and the cable was sliding behind the risers. So I tagged the Tensiometer (Out of Service) and turned it in to Parts and picked up a smaller one for doing the flight deck cables; which was an alternate [tensiometer] as called out in Engineering Notice-27-121 Revision-1. I also got the Tensiometer from the hangar tool box that was a GSE-074 for the wings and fuselage. I checked the chart in the smaller tensiometer box to see what riser to use with the cables I was measuring. One cable was a 3/32' [of an inch] and needed a Number 1 and one was a 5/32' and it needed a Number 2-C riser. I then proceeded to check the tension again in the flight deck but was told to stop due to a Brake Check that needed to be accomplished for troubleshooting and Avionics' work that needed to be completed. So I stopped work in the flight deck and proceeded to the wings and fuselage areas where the temperature had raised again; so I had to recheck the cable chart again for the right load. During the adjustment I noticed the load kept changing by as much as 20-30-lbs with only 1/2 of a twist of the [cable] turnbuckle. I started looking up and down the cables and found one of the Sheetmetal people was sitting between the [Cabin] seat tracks working and had his feet resting on the aileron cables. So I told him to put his feet somewhere else [because they] were giving me high [tension] readings. By that time it was shift change so I proceeded to gather up my stuff and documented what I had completed and went home.When I returned the next day I picked up where I left off. I started off [by] running the Flight Control cables through the full range of movement and then repined the cables. I proceeded to check the temperature and check the charts for the proper load. The temperature had dropped so I had to re-due everything from the day before and start over. I adjusted the cables in the flight deck area; [and] then the wings and fuselage; then I pulled the rig pins and ran the aileron cables through; rechecked all the cables and had at least one cable per sector bad. Again I checked the temperature; readjusted the cable tension; ran the aileron cables through the range of movement and found them to be out of range. With all the work going on in the aircraft my Lead Mechanic noticed I was getting frustrated so he had me explain what the problem was and where I was in the task; so I could turn it over to someone else. When the plane flew [approximately] eight days later; it had aileron problems. Ailerons would not operate correctly. The next day I came to work and saw the aileron cable access panels were open and found out what had happened. I talked to some of the mechanics; I found that I used the right tools and chart to start with; but when I used the alternate tensiometer I did not cross reference the load in the AMM to the chart that was in the tensiometer box; which caused me to overload the flight deck cables. [Recommend] finding a Tensiometer that is usable for all the aircraft cables and will fit in the area of the flight deck; this should minimize the chance of misreading the load limits of the cables. An Aircraft Maintenance Technician (AMT) was informed that an Embraer aircraft was unable to engage the Aileron Trim System during a flight test after he had accomplished an Aileron Control Cable rigging Task Card.